The physiologic role of human placental lactogen in maternal and fetal metabolism during pregnancy is unclear and the specific factors regulating the secretion of human placental lactogen are unknown. Numerous studies have demonstrated aberrations in human placental lactogen secretion in several pathologic conditions of pregnancies (diabetes mellitus, pre-eclampsia, etc.) and a decline in the maternal human placental lactogen concentration during pregnancy is associated with an increased risk of fetal morbidity and mortality. The objective of this proposal is 1) to study the effects of human placental lactogen on maternal and fetal carbohydrate, lipid, and protein metabolism during pregnancy using the sheep as an animal model; 2) to study the secretion of human placental lactogen in the normal and abnormal human placenta in organ culture; 3) to isolate and characterize ovine placental lactogen, 4) to study the physiologic role of ovine placental lactogen during pregnancy in the sheep, and 5) to correlate the in vitro studies of placental lactogen secretion to in vivo studies in the sheep. In preliminary studies from this laboratory, glucose has been found to modulate the secretion of human placental lactogen in organ culture.